When filling bags with a pourable material, it is desirable, on the one hand, to fill the bags quickly and, on the other hand it is necessary to dispense accurate amounts, because it is impermissible to fill the bags with less than the nominal amount and it is uneconomical to allow too great a scatter of the amount contained in a bag above the nominal value. The two requirements in respect of a rapid filling procedure on the one hand and accurate dispensing on the other hand contradict one another because the former requires a large flow of material and the latter a small flow of material. This is the reason why the bags to be filled are filled quickly up to an amount of 90 to 95% of the nominal amount, involving a large flow of material, with the scatter of the result achieved being allowed to be relatively large, and subsequently, a small flow of material ensures accurate filling, with only a few percentage points being above the nominal amount.
One problem of prior art filling techniques occurs when powdery materials are enriched with air during the filling operation. This happens automatically during the travel of the material from the bunker via a weighing machine into the feeding funnel, especially if the feeding funnel contains a stirring mechanism whose purpose it is to maintain the flowing ability of the material. This is disadvantageous in that it is necessary to extract the air from the measured material contained in the bag before the bag is closed. Air extraction probes for this purpose are disclosed in German publication DE 34 14 218 C2 for example. During the deaerating process, the volume of the material filled into the bag is reduced, so that there is an excessively long bag flap which first has to be shortened before the bag is closed.